Effect Of Repeated Freeze-Thaw Cycles On Goat Quality

Temperature fluctuation generally occurs during meat transportation, storage or consumption, which results in repeated freeze-thaw process. Biochemical and physicochemical changes during freeze-thaw cycles would result in quality deterioration. Therefore, the present study is designed to investigate changes of ultrastructure, water mobility, protein rheology and fatty acids profiles in goatmeat during freeze-thaw cycles.Chapter1Effect of freeze-thaw cycles on eating and technological qualities of goat meatThe changes of thawing loss, pH, colors, water-holding capacity, tenderness, solubility of proteins, TBA values, water-holding capacity and texture of minced products were measured after different freeze-thaw cycles. The results showed that as the freeze-thaw cycles increased, pH decreased firstly, then increased after15freeze-thaw cycles; L and a*decreased(p<0.05), b*decreased firstly, then increased after15freeze-thaw cycles; thawing loss increased gradually(p<0.05), pressing loss and cooking loss decreased gradually(p<0.05), pressing loss+thawing loss and cooking loss+thawing loss increased gradually(p<0.05); shear force decreased gradually(p<0.05); Total protein solubility and myofibrillar protein solubility decreased firstly, then increased after5freeze-thaw cycles(p<0.05); sarcoplasmic protein solubility decreased firstly, then increased after15freeze-thaw cycles (p<0.05);TBA increased (p<0.05). With the freeze-thaw cycles increased, pressing loss of sausage increased firstly, then decreased after5freeze-thaw cycles, and increased after10freeze-thaw cycles; Hardness and chewiness of the meat sausage decreased firstly(p<0.05), then increased after5freeze-thaw cycles (p<0.05), and decreased after5freeze-thaw cycles finally(p<0.05). Cohesiveness and resilience of the meat suasage decreased(p<0.05). PCA analysis showed that eating and technological qualities of goatmeat had no significant changes between5and10freeze-thaw cycles. Therefore, freeze-thaw cycles had significant effect on goatmeat quality.Chapter2Effect of freeze-thaw cycles on physicochemical, biochemical and ultrastructural characteristcis of goatmeatChanges of ultrastructure, water mobility, protein rheology and fatty acid profile of goatmeat were investigated after different freeze-thaw cycles. The results showed that as the freeze-thaw cycles increased, frame structure of sarcomers disappeared, endomysium was destroyed, fiber diameter decreased gradually(p<0.05), sarcomer length decreased firstly, then increased after15freeze-thaw cycles(p<0.05); T21release times of meat decreased gradually(p<0.05), T22release times decreased firstly, then increased after5freeze-thaw cycles, and decreased after10freeze-thaw cycles (p<0.05); G42increased firstly, then decreased after10freeze-thaw cycles(p<0.05); saturated fatty acid and monounsaturated fatty acid content decreased firstly,then increased after1freeze-thaw cycles(p<0.05), polyunsaturated fatty acids content increased gradually.(p<0.05).In conclusion, quality deterioration took place during freeze-thaw cycles due to significant change of ultrastructure, water mobility, rheology of protein and fat oxidation and hydrolysis of goatmeat.